We have demonstrated that 7,12-dimethylbenz (a) anthracene (DMBA) interacts with progesterone serum carrier and uterine cytosol receptor proteins. DMBA administration (1 mg/day for 3 days) reduces the estrogen receptor levels and increases progesterone receptor levels within 20 days in rabbit uterine cytosol. DMBA is a mild progestational agent and has a weak estrogenic action in a modified Clauberg's assay. Progestational activity of DMBA will be confirmed using a diciduoma maintenance assay. We will investigate whether other polycyclic hydrocarbons have a similar effect on uterus. Next, we will investigate the effect of polycyclic hydrocarbons on mammary tissue with respect to cytosol estrogen and progesterone receptor levels and histological changes induced in the tissue. In the event the histology showed induced variations in cell types, then, we will separate the cell types by centrifuging in albumin gradients and analyze the individual cell populations. A similar investigation will be performed also with endometrial cells. Additionally we will investigate to establish whether estrogens or progestins can reverse the effects induced by polycyclic hydrocarbons.